The exact size and capability of China's nuclear arsenal is difficult to measure, but as of 1993 it was believed to have around 434 active warheads.

The following information is based on intelligence gathered by international sources including the Nuclear Weapons Handbook, the Federation of American Scientists and the Campaign for Nuclear Disarmament.

Weapon types

Nuclear explosions release energy in three different ways - through the blast, heat and radiation.

The first nuclear weapons developed were the atomic bombs, developed by the US during World War II.

Thermonuclear weapons - formerly known as hydrogen bombs - superseded the atom bomb and have proved far more powerful.

Neutron bombs or "enhanced radiation" weapons were first developed as an advanced tactical weapon to form part of a "limited strike" arsenal. The land missiles

China's land-based nuclear missiles carry thermonuclear warheads which use a self-sustaining chain reaction of hydrogen fusion to produce a massive blast of light, heat, and fallout.

The shockwave alone can completely destroy everything in a radius of several miles while the light will blind people standing 20 miles away.

China carried out its first thermonuclear detonation on 17 June 1967.

Ballistic missiles

The DF series of medium range ballistic missiles forms the backbone of China's nuclear arsenal.

DF-5: Capable of reaching Europe or North America

According to the Nuclear Weapons Handbook, China has produced around 170 DF series missiles.

The DF-3a, carries a three-megatonne warhead and has a range of about 2,800km. Its theoretical targets included US military bases in the Philippines.

The first test launch of a DF-3a was on Chairman Mao's 63rd birthday in 1966 and it was fully deployed by 1971.

The DF-4, developed from the DF-3a, increased China's intercontinental reach to around 4,750km - enough to reach Moscow.

Greater ranges

The development of the DF-5 in the late 1960s aimed to produce a missile with a range of up to 12,000km.

China proved the reliability of the rocket stage of the missile by launching several satellites in the late 1970s.

Scientists believe that only four DF-5s have been deployed - but each has a warhead of at least four megatonnes and the range to reach North America, Russia or Europe.

Submarine launch

JL-1: Submarine and mobile land use

China's submarine launch missile, the JL-1, "the Giant Wave", is ejected from its launch pod before it fires its engines - a major technical advance. It was first tested in October 1982.

Despite this success, its uses are restricted by China's geographical position in relation to its potential adversaries and the missile's limited range of 1,800km.

The slim design of the missile is also the foundation of China's mobile land-launch missiles which were deployed as the DF-21 in 1985.

China's atom bomb

Early technology: But great advances in recent years

Where thermonuclear weapons use fusion, atom bombs harness the energy of fission, the splitting of heavy elements such as plutonium and uranium.

This releases thermal energy, gamma radiation and more material to create a chain reaction.

China's first ever nuclear test of a three-megatonne weapon at Lap Nor in 1964 heralded its arrival as a nuclear power.

China maintains a fleet of at least 100 nuclear bombers but the programme has been largely superseded by missile development.

Tactical nuclear weapons

China's announcement that it has developed miniature warhead techniques and the neutron bomb are arguably the first official evidence of a tactical weapons programme to be used in limited combat scenarios.

Miniaturisation means that lower yields of nuclear material can be used without necessarily affecting the amount of energy released.

This is achieved by "implosion" technique. A conventional explosive is placed around the plutonium or uranium 235. When it detonates, it compresses the radioactive element so much that the "critical size" of material needed for a nuclear explosion is greatly reduced.

If it has developed miniature warheads, it means that China will have the capability of delivering more than one warhead from the same rocket missile.

The Cox Report into China's nuclear expionage in the USA said that Beijing acquired details of its most sophisticated current warhead - the W-88.

This miniature tapered warhead is deployed with the Trident D-5 submarine launch missile

In terms of neutron capability, nobody knows exactly what China has developed but prior to the Cox Report into nuclear espionage Washington said that it believed Beijing ordered a neutron bomb test in 1988.

If the Cox Report conclusions are correct, China stole the blueprints to the W-70 warhead, the basis of a neutron bomb, as long ago as the late 1970s.

Scientists produced small numbers of the W-70 warhead, designed for use with the Lance tactical missile over battlefields.